Hot screen printing machine

ABSTRACT

A practical and useful hot screen printing machine having at least one rotatable cylindrical printing drum comprising a flexible plane heater on the outer surface thereof and an electrical insulating layer surrounding the plane heater.

United States Patent Tsuboi et al. 1 Mar. 14, 1972 [54] HOT SCREENPRINTING MACHINE [56] References Cited [72] Inventors: Masayoshi Tsuboi;Tnmeo KOIIIIII'I; UNITED STATES PATENTS Sigerll Tezulta; Mi Konrlo, allof Asaka,

Japan 2,679,572 5/1954 Workman ..2 19/469 3,310,655 3/1967 Ha er, Jr.

131 Asslgneez Fu i Photo Film Co., Ltd., Kanagawa, 3,520,747 7/19703,401,439 9/l968 Staats et al..... [22] Filed: Aug. 7, 1970 3,471,68310/1969 Bogue l 2 pp NOJ 62,115 3,469,077 9/1969 Petersen et al...2l9/469 Primary Examiner-C. L. Albn'tton [30] Foreign ApplicationPriority Data Attorney-Sughrue, Rothwell, Mion, Zinn and Macpeak Aug.11, 1969 Japan ..44/63389 ABSTRACT [52] US Cl. 319/216, 100/93 RP,219/469 A practical and useful hot screen printing machine having at 51..l'l05b 1/00 least one rotatable cylindrical printing drum comprising aflex- 19/216, 244, 469471. ible plane heater on the outer surfacethereof and an electrical insulating layer surrounding the plane heater.

4 Claims, 4 Drawing Figures PATENTEDMAR 14 I972 TEMPERATURE (C}TEMPERATURE (C) TIME 2 (MINUTES) 3 INVENTORS MASAYOSHI TSUBOI TSUNEOKOMURA SIGERU TEZUKA ASAJI KONDO II OT SCREEN TING MACHINE BACKGROUNDOFTHE INVENTION The present invention relates to .a hot screen printingmachine. More particularly, the present invention is concerned with ahot screen printing :machine comprising a flexible plane heater on theprinting drum.

The heating of the printing drum inpresently known hot screen printingprocesses has-been generally conducted indirectly by means .of anelectric'heater such as nicrome wire, infrared rays, hot air .or steam.

In a series of studies of the hot screenprinting process, we have foundthat an excellent print can be easily obtained in the combination ofthe-hitherto known screen printing machine having a printing drum, forexample, single, or double drum type printer, with :a plane heateras theheating source.

SUMMARY OF THE INVENTION That is to .say, the hot screen printingmachine of .the present invention comprises at least one rotatablecylindrical printing drum provided with aneleetric insulating layersurrounding a plane heater having electrodes on the outersurface of theprinting drum thereof.

An object of the present invention isto provide :an improvement in ascreen printing .macln'ne. Another object of the present invention is toprovide a practical and useful hot screen printing machine asmentionedhereinafter and illustrated in the drawings.

Another object of the present invention is to propose a practical screenprinting processsuitable to obtain printed matter with a very clearimagein .an easy operation by using the improved hot screen printing machine.

BRIEF DESCRIPTION OF THEDRAWINGS FIG. 1 is a perspective view, partly insection, of a portion of the printing drum of the hot screenprintingmachine of the present invention; and v FIG. 2 is another perspectiveview of a portion of the hot screen printing machine of the presentinvention.

FIGS. 3 and 4 are respectively temperature versus voltage and timegraphs for the heater of the present invention.

DESCRIPTION OF THE'PREFERRED EMBODIMENT FIG. 1 illustrates a printingdrum l for use inthe single drum type screen printing machine of thepresent invention. The drum 1 comprises a plane heater 3 on the outersurface thereof, and an insulating layer2 disposed inwardly of theheater 3.

As shown in FIG. 2, electrodes 44 and 4b, substantially parallel to thecenter shaft 6, are disposed on the surface of the plane heater 3. Leadwires sa and 512 connected to the electrodes 4a and 4b respectively, arecontacted with circular electrodes 8 and 9, respectively, which arepositioned at the side of the printing drum 1 and separated by anannular insulating layer 7. The circular electrodes 8 and 9 areconnected with a source of electricity (not shown-)by current collectorsI and 11.

In this case, the prevention of an electric shock may be easily effectedby providing an insulating layer 12 on the surface of the plane heater3.

Alternatively, the electrodes 4a and 4b may be positioned along one endof the circumference of the printing drum 1.

Although the drawing illustrates a single drum type printing machine, adouble drum type may be utilized in accordance with the teachings of thepresent invention.

The other parts in the hot screen printing machine according to thepresent invention are similar to the hitherto known screen printingmachine; namely, a hand-operated lever or an automatic rotatingapparatus (not shown) is provided for rotating the drum shaft 6, and apressure roller 13 is in engagement with the printing drum 3.

The :plane heater 3 may be formed, for example, of a moldedplasticmaterial of any suitable type. As illustrative examples, a film-formingpolymer may be mixed with an electrically conductive material, or such apolymer may be applied uniformly with an electrically conductivematerial onto a suitable base, such as glass cloth, the polymerpreferably being of the heat-resistant type. Also, it may be possible touse a cloth made up of an electrically conductive fiber.

The electrically conductive material for the plane heater 3 may beselected from the group consisting of carbon black or grafted carbon,aluminum powder, silver powder and copper power, used singularly or incombination. A plane heater having a thickness of 20 microns to 2 mm. ispreferable so that it is sufficiently flexible to be easily wound aroundthe printing drum 1.

The insulating layer 2, for example, may be selected from the groupsconsisting of polyethylene terephthalate film, cellulose triacetatefilm, felt or sponge.

The temperature of the ink layer used in the hot screen printing machineof the present invention should be below the limit of heat resistancetemperature of the screen stencil and it is usuallyat a temperature lessthan about 90 C. Since the surface temperature of the plane heater 3does not have to be more than 20 C. higher than the temperature of theink layer, the heater 3 may generally be maintained at a temperatureless than about 1 10 C.

The plane heater 3 may be charged with either a direct current or analternating current, but usually an alternating current is preferable. Apair or more of the electrodes 4a and 4b parallel to the shaft 6 of saidprinting drum 1, or a pair or more of the electrodes along thecircumference of the drum, may be equipped and charged with a sufficientvoltage such that said plane heater 3 is maintained at the desiredtemperature.

The relation of the charged voltage with the temperature in case wherethe plane heater 3, having 170 microns thickness, prepared by adding 20percent by weight of carbon black to cellulose triacetate, is chargedthrough electrodes (25 cm. distance) is illustrated in FIG. 3. Therelation between the temperature and the time in case of charging theelectrodes with v. is illustrated in FIG. 4. As is understood from FIGS.3 and 4, it requires only about seconds for reaching 80 percent of thethermal variation from room temperature 26 to 60 C., namely, 53.2 C.,and the thermal fluctuation on the surface of said plane heater 3 iswithin 3 C.

The application of the plane heater 3 to the hot screen printing machineis markedly advantageous in view of the simplicityof the attachment ofthe heater to the printing drum, owing to its flexibility in addition tothe possibility of rapid elevation of temperature with maintaining auniform thermal distribution.

The printing machine of the present invention makes it possible to usean ink which is at a solid state at ordinary temperatures, due to thepossibility of printing at a temperature higher than an ordinarytemperature, thereby conducting the printing operation with lessstaining of hands, etc., during the operation.

In the practice of screen printing by means of the hot screen printingmachine of the present invention, an ink for screen printing is directlyapplied from a tube or a can to the insulating film l2 overlying theplane heater, and the printing operation can be run at a constanttemperature elevated from ordinary temperatures.

With respect to the supply of the ink, a method of using an ink sheet isvery superior to the above. The term ink sheet" is used herein isintended to cover one prepared by applying an ink on a sheet of asupport inactive to the ink or a support that is not permeated by theink at a temperature range imparting the fluidity. If an ink, which issolid at ordinary temperatures, but fluid only when heated to atemperature higher than an ordinary temperature, is used for the screenprinting machine of the present invention, there is no fear of staininghands and clothes with the ink, other than when actually printing.

Consequently, if a solid ink having a fluidity desirable for printing ata temperature ranging from 50 to 70 C. is employed in the hot screenprinting machine of the present invention, the solid ink can be easilyheated to a temperature imparting the desirable fluidity within 1 to 3minutes, and thereby the screen printing can be efi'ectively conductedin a conventional screen printing stencil.

The following specific examples are intended to show the nature of theinvention without limiting it to the examples themselves.

EXAMPLE I A printing drum of a single drum type rotary mimeographiccopying machine (for example, Sekisei Rotary Copying Machine) wasremodeled as follows.

A polyester film having microns thickness was wound around an aluminumprinting drum having 4.5 cm. in radius to insulate the drum, and acellulose triacetate film (170 microns thickness) containing percent byweight of carbon black content as the plane heater was layed on thepolyester film layer, and further a polyester film having 100 micronsthickness as an insulator was wound around the heater.

Aluminum foil having 0.5 cm. in width was adhered in the directionparallel to a shaft of the printing drum to both ends cm. distance) ofthe plane heater by using an electrically conductive paste to makeelectrodes respectively, and lead wires and brush type currentcollectors were connected to the electrodes.

When the hot screen printing machine was charged with 80 v. ofalternating current, the surface temperature became 54.5" C. within 2minutes.

An ink sheet, which was prepared by applying to a cellophane sheet X40cm.) so as to leave 4 cm. of the circumference free, 15 g. of ink madeup mainly of 90 parts of paraffin, 3 parts of cellulose flock and 7parts of carbon black, and was at a solid state at an ordinarytemperature under 60 C., was set on the printing drum of the hot screenprinting machine and, after laying a mimeographic stencil paper cut witha typewriter on the ink sheet, the printing was started while beginningto impart fluidity to the ink.

In this process, 100 sheets of clearly printed matter were produced.

EXAMPLE 2 The plane heater used was prepared by applying an 80 percentconcentration dispersion of grafted carbon (produced by Nippon GasChemical Industries, Ltd.) containing 50 percent by weight of carbonblack onto a glass cloth and drying it. The hot screen printing machinewas made up as in example 1.

In this case, since the glass cloth served as an insulating layer forthe aluminum drum, the polystyrene film having 15 microns in thicknesswas not required.

When the machine was charged with 70 v. of alternating current throughthe electrodes (25 cm. distance), the surface temperature became 70 C.within 25 minutes.

As the ink supplying source, ,there was used an ink'sheet prepared byapplying a colorless ink containing a dye base to a support, and thenthe hot screen printing was conducted using clay paper, applied with anacid clay, as the printing paper.

The term dye base" used herein is intended to cover a leuco pigment, alactone derivative of pigment, a lactam derivative of pigment and thelike.

The colorless ink was prepared by mixing l.5 g. of crystal violetlactone, 15 g. of diphenyl tetrachloride, 20 g. of triphenyl chlorinateand 30 g. of paraffin having a melting point of 62 C. under heating.

We claim:

1. A hot screen printing machine comprising at least one rotatablecylindrical drum;

a flexible sheet of electrically conductive material wrapped around thedrum and capable of generating heat comprising a heat resisting polymerfilm containing a material selected from the group consisting of carbonblack, grafted carbon, aluminum powder, silver powder, and

PP. l J an electrically insulating layer on the outside surface of thedrum 7 and above the sheet of electrically conductive material andformed of a material selected from the group consisting of polyethyleneterephthalate film, cellulose triacetate film, felt and sponge, and

means for supplying electricity to the heat generating flexible sheetincluding a pair of electrodes positioned parallel to the drum andextending across the surface of the flexible sheet beneath theinsulating layer.

2. A hot screen printing machine as in claim 1, where the means forsupplying electricity further includes lead wires and brush type currentcollector means connected to the electrodes and positioned at one end ofthe drum radially inward of the electrodes.

3. A hot screen printing machine as in claim 2, where the thickness ofthe flexible sheet isbetween 20 microns and 2 mm.

4. A hot screen printing machine as in claim 3, where the temperature ofthe flexible sheet will remain within 3 C. at steady state and theelectrodes will be positioned approximately 25 cm. apart on the flexiblesheet.

1. A hot screen printing machine comprising at least one rotatablecylindrical drum; a flexible sheet of electrically conductive materialwrapped around the drum and capable of generating heat comprising a heatresisting polymer film containing a material selected from the groupconsisting of carbon black, grafted carbon, aluminum powder, silverpowder, and copper powder; an electrically insulating layer on theoutside surface of the drum and above the sheet of electricallyconductive material and formed of a material selected from the groupconsisting of polyethylene terephthalate film, cellulose triacetatefilm, felt and sponge, and means for supplying electricity to the heatgenerating flexible sheet including a pair of electrodes positionedparallel to the drum and extending across the surface of the flexiblesheet beneath the insulating layer.
 2. A hot screen printing machine asin claim 1, where the means for supplying electricity further includeslead wires and brush type current collector means connected to theelectrodes and positioned at one end of the drum radially inward of theelectrodes.
 3. A hot screen printing machine as in claim 2, where thethickness of the flexible sheet is between 20 microns and 2 mm.
 4. A hotscreen printing machine as in claim 3, where the temperature of theflexible sheet will remain within 3* C. at steady state and theelectrodes will be positioned approximately 25 cm. apart on the flexiblesheet.